extensions-tool: Add common option to silence errors

Error reporting is useful when used interactively, but often undesirable
when used in scripts. Account for that with a common --quiet option,
which is more convenient than redirection stderr to /dev/null.

https://gitlab.gnome.org/GNOME/gnome-shell/issues/2391

subprojects/extensions-tool/man/gnome-extensions.txt

@@ -42,6 +42,13 @@ DESCRIPTION
 *gnome-extensions* is a utility that makes some common GNOME extensions
 operations available on the command line.
 
+COMMON OPTIONS
+--------------
+All commands except for *help* and *version* handle the following options:
+
+*--quiet*, *-q*::
+Do not print error messages
+
 COMMANDS
 --------
 *help* ['COMMAND']::

subprojects/extensions-tool/src/command-create.c

@@ -262,6 +262,7 @@ handle_create (int argc, char *argv[], gboolean do_help)
   g_option_context_set_help_enabled (context, FALSE);
   g_option_context_set_summary (context, _("Create a new extension"));
   g_option_context_add_main_entries (context, entries, GETTEXT_PACKAGE);
+  g_option_context_add_group (context, get_option_group ());
 
   if (do_help)
     {

subprojects/extensions-tool/src/command-disable.c

@@ -56,6 +56,7 @@ handle_disable (int argc, char *argv[], gboolean do_help)
   g_option_context_set_help_enabled (context, FALSE);
   g_option_context_set_summary (context, _("Disable an extension"));
   g_option_context_add_main_entries (context, entries, GETTEXT_PACKAGE);
+  g_option_context_add_group (context, get_option_group());
 
   if (do_help)
     {

subprojects/extensions-tool/src/command-enable.c

@@ -56,6 +56,7 @@ handle_enable (int argc, char *argv[], gboolean do_help)
   g_option_context_set_help_enabled (context, FALSE);
   g_option_context_set_summary (context, _("Enable an extension"));
   g_option_context_add_main_entries (context, entries, GETTEXT_PACKAGE);
+  g_option_context_add_group (context, get_option_group());
 
   if (do_help)
     {

subprojects/extensions-tool/src/command-info.c

@@ -78,6 +78,7 @@ handle_info (int argc, char *argv[], gboolean do_help)
   g_option_context_set_help_enabled (context, FALSE);
   g_option_context_set_summary (context, _("Show extensions info"));
   g_option_context_add_main_entries (context, entries, GETTEXT_PACKAGE);
+  g_option_context_add_group (context, get_option_group());
 
   if (do_help)
     {

subprojects/extensions-tool/src/command-install.c

@@ -183,6 +183,7 @@ handle_install (int argc, char *argv[], gboolean do_help)
   g_option_context_set_help_enabled (context, FALSE);
   g_option_context_set_summary (context, _("Install an extension bundle"));
   g_option_context_add_main_entries (context, entries, GETTEXT_PACKAGE);
+  g_option_context_add_group (context, get_option_group());
 
   if (do_help)
     {

subprojects/extensions-tool/src/command-list.c

@@ -150,6 +150,7 @@ handle_list (int argc, char *argv[], gboolean do_help)
   g_option_context_set_help_enabled (context, FALSE);
   g_option_context_set_summary (context, _("List installed extensions"));
   g_option_context_add_main_entries (context, entries, GETTEXT_PACKAGE);
+  g_option_context_add_group (context, get_option_group());
 
   if (do_help)
     {

subprojects/extensions-tool/src/command-pack.c

@@ -480,6 +480,7 @@ handle_pack (int argc, char *argv[], gboolean do_help)
   g_option_context_set_help_enabled (context, FALSE);
   g_option_context_set_summary (context, _("Create an extension bundle"));
   g_option_context_add_main_entries (context, entries, GETTEXT_PACKAGE);
+  g_option_context_add_group (context, get_option_group());
 
   if (do_help)
     {

subprojects/extensions-tool/src/command-prefs.c

@@ -89,6 +89,7 @@ handle_prefs (int argc, char *argv[], gboolean do_help)
   g_option_context_set_help_enabled (context, FALSE);
   g_option_context_set_summary (context, _("Opens extension preferences"));
   g_option_context_add_main_entries (context, entries, GETTEXT_PACKAGE);
+  g_option_context_add_group (context, get_option_group());
 
   if (do_help)
     {

subprojects/extensions-tool/src/command-reset.c

@@ -1,4 +1,5 @@
 /* command-reset.c
+  g_option_context_add_group (context, get_option_group());
  *
  * Copyright 2019 Florian Müllner <fmuellner@gnome.org>
  *
@@ -56,6 +57,7 @@ handle_reset (int argc, char *argv[], gboolean do_help)
   g_option_context_set_help_enabled (context, FALSE);
   g_option_context_set_summary (context, _("Reset an extension"));
   g_option_context_add_main_entries (context, entries, GETTEXT_PACKAGE);
+  g_option_context_add_group (context, get_option_group());
 
   if (do_help)
     {

subprojects/extensions-tool/src/command-uninstall.c

@@ -71,6 +71,7 @@ handle_uninstall (int argc, char *argv[], gboolean do_help)
   g_option_context_set_help_enabled (context, FALSE);
   g_option_context_set_summary (context, _("Uninstall an extension"));
   g_option_context_add_main_entries (context, entries, GETTEXT_PACKAGE);
+  g_option_context_add_group (context, get_option_group());
 
   if (do_help)
     {

subprojects/extensions-tool/src/common.h

@@ -45,6 +45,8 @@ typedef enum {
   DISPLAY_DETAILED
 } DisplayFormat;
 
+GOptionGroup *get_option_group (void);
+
 void show_help (GOptionContext *context,
                 const char     *message);
 

subprojects/extensions-tool/src/main.c

@@ -49,6 +49,39 @@ extension_state_to_string (ExtensionState state)
   return "UNKNOWN";
 }
 
+static void
+print_nothing (const char *message)
+{
+}
+
+static gboolean
+quiet_cb (const gchar  *option_name,
+          const gchar  *value,
+          gpointer      data,
+          GError      **error)
+{
+  g_set_printerr_handler (print_nothing);
+  return TRUE;
+}
+
+GOptionGroup *
+get_option_group ()
+{
+  GOptionEntry entries[] = {
+    { .long_name = "quiet", .short_name = 'q',
+      .description = _("Do not print error messages"),
+      .arg = G_OPTION_ARG_CALLBACK, .arg_data = &quiet_cb,
+      .flags = G_OPTION_FLAG_NO_ARG | G_OPTION_FLAG_IN_MAIN },
+    { NULL }
+  };
+  GOptionGroup *group;
+
+  group = g_option_group_new ("Common", "common options", "common options", NULL, NULL);
+  g_option_group_add_entries (group, entries);
+
+  return group;
+}
+
 void
 show_help (GOptionContext *context, const char *message)
 {